Unsolved HDMI Display Not Recognizing Rpi SBC

[itsjuicetin]

I'm trying to set up my RPi as an SBC with my Duet 3MB6HC board but I'm having issues getting the RPi to be recognized by the HDMI display when the Duet board is powered on. Here's what I've tried so far:

Following the instructions listed here for 'SBC setup for Duet 3', these are the steps I've taken:

• Flashed the Rpi with a "2023-04-12-DuetPi.img" image onto an SD card
• Loaded the Rpi with the card, ensuring that no SD cards are in the Duet board
• Initially connected the Rpi 4b with the ribbon cable to the Duet with an HDMI display connected to the Rpi and an external 5V power supply to the Rpi (separate from the power supply going to the Duet board)
• At this point, the HDMI display did not recognize the Rpi
• Powered off the Duet board and powered on the Rpi again (i.e. only the Rpi was being powered) --> this time the Rpi WAS recognized by the display and the Duet Control web interface appeared on the display but with the following error: failed to connect to duet, please check your connection (DCS is not started)

My question is, why isn't the HDMI display recognizing the Rpi when the Duet board is powered on? I've gone through this entire process with a different Rpi 4b with the exact same results so I don't think it's an issue with the Rpi board and I've also been able to get an image on the HDMI display so I don't think it's an issue with the display or cable.

If you need any additional information, please let me know and I would be happy to provide. I'm a bit of a beginner when it comes to this Duet system/Raspberry Pi's in general but I'll do my best to follow any debugging steps provided. Thank you!

[chrishamm]

@itsjuicetin Maybe it takes too much power. Are you operating your RPi with a decent power supply? Some HDMI screens need special config.txt commands to get it to work, but that isn't specific to a Duet setup.

[itsjuicetin]

@chrishamm It's being provided power through a Canakit 5V power supply brick that came with the Pi so I'm thinking it might not be a power issue.

I messed around with things a little more and after powering on the Rpi FIRST and then the Duet board, I was able to get a connection to the HDMI display.

However, even though both the Duet and the Rpi are powered and connected to each other, I'm getting the same "Operation failed (Reason: Failed to connect to duet, please check your connection (DCS is not started)).

Any ideas on what the problem could be? When I open the Duet Web Control interface, I get a blue "Connecting..." loading bar with the error message as written above.

[chrishamm]

@itsjuicetin I suggest you have a look at this: https://github.com/Duet3D/DuetSoftwareFramework/wiki/SBC-Setup-Guide#troubleshooting The UI should display a reason why the main control application (DCS) could not be started. That info can be obtained from the logs, too.

Can you confirm that there is no microSD card in the Duet? Also, if you have a v1.02 MB6HC, you should have RRF v3.4.4+1 or newer installed. Older firmware versions with this board revision have a bug affecting SBC communication.